Showing papers by "Leslie Hyman published in 2012"

Factors associated with macular thickness in the COMET myopic cohort.

Abstract: Myopia is a risk factor for glaucoma, retinal detachments, and degenerative changes in the central retina, conditions which can lead to significant vision loss.1, 2 Because the prevalence of myopia is increasing, the economic and visual burden of these related diseases may also increase.3 It is therefore important to understand why the myopic eye seems to be more susceptible to disease. Some previous studies have utilized more traditional examination methods, such as binocular indirect ophthalmoscopy.4–6 However, retinal structures can now be visualized in vivo using optical coherence tomography (OCT). 7 The resolution of commercially available OCT systems is approximately 5 to 10 microns, allowing visualization of distinct layers within the retina.8 This technology allows more sensitive and standardized measures of the retina in the living eye, which should enhance our understanding of the pathophysiology of myopia and its relationship to the development of other ocular diseases. Previous OCT studies have suggested that macular thickness is associated with age, gender, ethnicity, axial length, and refractive error.9–21 These studies have used different instruments and algorithms and include populations that differ by age, gender, ethnicity, country of origin, and refractive status. Despite these differences, most 10,11,15–18 but not all 9,14 studies report that females have thinner maculas than males. In addition, persons of African descent have thinner central foveas and some quadrants of the outer foveal regions compared to other ethnic groups, with some variation among studies.9–15 Some OCT studies, mainly performed in Asia, have explored the potential relationship between macular thickness and axial length and/or amount of myopia.15–21 In these studies, increased axial length has been associated with thicker central foveas17–20 and some thinner quadrants in the para- and peri-foveal regions, 16–20 with one study finding no association.15 Results for refractive error are more mixed; some studies find that myopia is associated with a thicker central fovea and some thinner para- and peri-foveal quadrants, 18–21 while others find no association.15–17 No prior studies have included large numbers of myopic young adults of different ethnic backgrounds. Data from the Correction of Myopia Evaluation Trial (COMET) allow the investigation of macular thickness and related factors in a large, multi-ethnic group who were aged 6–11 years with low to moderate myopia when they enrolled in COMET in 1997 and aged 17–22 years at the time of OCT measurements, 11 years later. The purpose of this study is to determine whether macular thickness is related to ethnicity, gender, axial length and amount of myopia in a large cohort of myopic young adults, in which over one-quarter have high myopia (worse than –6.0 D). These data should enhance our understanding of factors associated with macular thickness in individuals with myopia, which has increased in prevalence in recent years to 40% of the population aged 12–54 years living in the United States.3

Intraocular Pressure and Central Corneal Thickness in the COMET Cohort

Abstract: The Correction of Myopia Evaluation Trial (COMET), a multi-center, randomized, double-masked clinical trial of ethnically diverse myopic children, evaluated the effect of progressive addition lenses vs. single vision lenses on myopic progression.1 After five years, when the clinical trial phase ended, COMET became a natural history study of risk factors for myopia progression and stabilization. While intraocular pressure (IOP) has been hypothesized as a risk factor for myopia development and progression,2–5 IOP measurements were not included in the original COMET protocol, but were taken in a subgroup of the COMET cohort at one of the clinical centers (Houston). No association was found between IOP and myopia at baseline or with 5- year myopic progression in this subset.6 However, a relationship between IOP and ethnicity was found, with higher pressures observed in African-Americans than in Hispanics and Whites. 6 Similar ethnic differences were also observed in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) study, with African-Americans having slightly higher IOP than Whites beginning at 10 years of age.7 One limitation of these prior data that may impact the interpretation of the IOP differences is the absence of central corneal thickness (CCT) measurements. CCT can impact tonometry results, with IOP underestimated in thinner corneas.8 CCT has also been reported in some studies to vary by ethnicity, with thinner CCT in African-American than in White9–11 or Hispanic children,9,11 but these populations included a range of refractive errors not limited to myopia and were younger than the COMET cohort. Hence, it is not known if ethnic-related differences in CCT may have contributed to the disparity in IOP found between ethnic groups in the COMET subset. In addition to the relationship of CCT with IOP and ethnicity, an association between CCT and refractive error has been reported. Thinner CCT values were observed in an ethnically diverse group of myopic children aged 0 to 17 years than in those with emmetropia or hyperopia (range −17.50D to +13.00 D with 64% between +3.00 and −1.00D).11 An inverse relationship between CCT and myopia, e.g., thinner CCT associated with increasing myopia, has also been described in young (22.2 ± 4.2 years) Asian adults.12 Understanding the relationship between refractive error and CCT may provide important information for myopic young adults seeking to reduce or eliminate their dependence on spectacles or contact lenses through keratorefractive surgery procedures that correct myopia by altering the shape and thickness of the cornea.13 CCT is a critical factor in determining the suitability of an eye for these refractive surgery procedures.13–14 The purpose of this report is to describe the distribution of and relationship between IOP and CCT in the ethnically diverse COMET cohort of myopic young adults and explore possible associations of IOP and CCT with ethnicity, magnitude of myopia, axial length (AL), vitreous chamber depth (VCD), and other ocular and demographic parameters. These data may provide guidance for clinical management of young adults and children with myopia, a population that represents a large portion of many eye care practices.